[clang-tools-extra] [clang-tidy] Adds do-while support to performance-inefficient-string-concatenation (PR #186607)

[Berkay Sahin via cfe-commits]

https://github.com/berkaysahiin updated https://github.com/llvm/llvm-project/pull/186607

>From d5a32e47e54a02783ebb2a584b4b81b3328e395c Mon Sep 17 00:00:00 2001
From: Berkay <berkaysahindev at gmail.com>
Date: Sat, 14 Mar 2026 20:22:39 +0300
Subject: [PATCH 1/2] [clang-tidy] Adds do-while support to
 performance-inefficient-string-concatenation

---
 .../InefficientStringConcatenationCheck.cpp            | 10 +++++-----
 clang-tools-extra/docs/ReleaseNotes.rst                |  4 ++++
 .../performance/inefficient-string-concatenation.rst   |  2 +-
 .../performance/inefficient-string-concatenation.cpp   |  6 ++++++
 4 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.cpp b/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.cpp
index 92e3220fdb817..1067fca289a2c 100644
--- a/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.cpp
@@ -53,11 +53,11 @@ void InefficientStringConcatenationCheck::registerMatchers(
     Finder->addMatcher(cxxOperatorCallExpr(anyOf(AssignOperator, PlusOperator)),
                        this);
   } else {
-    Finder->addMatcher(
-        cxxOperatorCallExpr(anyOf(AssignOperator, PlusOperator),
-                            hasAncestor(stmt(anyOf(cxxForRangeStmt(),
-                                                   whileStmt(), forStmt())))),
-        this);
+    Finder->addMatcher(cxxOperatorCallExpr(anyOf(AssignOperator, PlusOperator),
+                                           hasAncestor(stmt(anyOf(
+                                               cxxForRangeStmt(), whileStmt(),
+                                               forStmt(), doStmt())))),
+                       this);
   }
 }
 
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 4b207609d598d..a3714736aa988 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -315,6 +315,10 @@ Changes in existing checks
 
   - Fixes false negatives when using ``std::set`` from ``libstdc++``.
 
+- Improved :doc:`performance-inefficient-string-concatenation
+   <clang-tidy/checks/performance/performance-inefficient-string-concatenation>` check by
+   adding support for detecting inefficient string concatenation in ``do-while`` loops.
+
 - Improved :doc:`performance-inefficient-vector-operation
   <clang-tidy/checks/performance/inefficient-vector-operation>` check by
   correctly handling vector-like classes when ``push_back``/``emplace_back`` are
diff --git a/clang-tools-extra/docs/clang-tidy/checks/performance/inefficient-string-concatenation.rst b/clang-tools-extra/docs/clang-tidy/checks/performance/inefficient-string-concatenation.rst
index 92b6b4e0370d6..1dacf91389154 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/performance/inefficient-string-concatenation.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/performance/inefficient-string-concatenation.rst
@@ -55,5 +55,5 @@ Options
 
 .. option:: StrictMode
 
-   When `false`, the check will only check the string usage in ``while``, ``for``
+   When `false`, the check will only check the string usage in ``while``, ``do-while``, ``for``
    and ``for-range`` statements. Default is `false`.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/performance/inefficient-string-concatenation.cpp b/clang-tools-extra/test/clang-tidy/checkers/performance/inefficient-string-concatenation.cpp
index 72080ed39e59b..adc37e4c4bedf 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/performance/inefficient-string-concatenation.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/performance/inefficient-string-concatenation.cpp
@@ -32,5 +32,11 @@ int main() {
     f(mystr2 + mystr1);
     mystr1 = g(mystr1);
   }
+
+  do {
+    mystr1 = mystr1 + mystr2;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: string concatenation results in allocation of unnecessary temporary strings; consider using 'operator+=' or 'string::append()' instead
+  } while (0);
+
   return 0;
 }

>From bdb55a574c2d4f3d820e1cff57efaf0f7530db20 Mon Sep 17 00:00:00 2001
From: Berkay <berkaysahindev at gmail.com>
Date: Sat, 14 Mar 2026 20:45:50 +0300
Subject: [PATCH 2/2] [clang-tidy] Fix typo in the release note entry

---
 clang-tools-extra/docs/ReleaseNotes.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index a3714736aa988..cc7418b973277 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -316,7 +316,7 @@ Changes in existing checks
   - Fixes false negatives when using ``std::set`` from ``libstdc++``.
 
 - Improved :doc:`performance-inefficient-string-concatenation
-   <clang-tidy/checks/performance/performance-inefficient-string-concatenation>` check by
+   <clang-tidy/checks/performance/inefficient-string-concatenation>` check by
    adding support for detecting inefficient string concatenation in ``do-while`` loops.
 
 - Improved :doc:`performance-inefficient-vector-operation